The present invention relates to the transportation of sheet stock in printers, preferably in matrix printers with separate tangential feeding of endless sheet or web material and of individual sheets towards the printing platen under utilization of pressure rolls which hold the respective sheet stock against the printing platen.
Printers of the type to which the invention pertains must be amenable to accommodate different types of material to be printed on, whereby various sheet material may be differently wide. The feeding of individual sheets and of one or more endless webs hold different problems. Moreover, it is desirable to provide for some automatic changeover from one kind of stock to the other and it is also necessary to avoid concurrent feeding of endless sheet stock and individual pieces of print material.
The German printed patent application No. B2717758 describes a typewriter in which individual sheets, as well as endless sheet stock is fed from one and the same side into the machine, and an automatic changeover is accommodated through the use of a channel in which the endless sheet stock is maintained in a waiting and stopping position under utilization of its own drive. At the end of the channel, a switch is provided which extends over the entire length of the drum shaped printing platen and which blocks either the adjoining path for individual sheets or the channel exit for the endless sheet or web. The switch is operated therefore, whenever a changeover from one kind of print stock to the other is desirable. The changeover, of course, is carried out through appropriate control structure. The problem exists however that printers, particularly matrix printers provide specific situations which render feeding of the different material of sheet stock from the same side impractical or even impossible.
The European Pat. No. B19676 discloses a transport device for print sheet stock in matrix printers using different kinds of stock, such as continuous strips, individual cards, document paper of different width and the like, and different transport mechanisms are provided which are associated with a common printer proper. However, this particular solution is suitable only for internal sheet stock wound on an internal spool and for external print material such as checks or the like.